BUG #14954: fresh install of postgresql-server 9.6.6-3PGDG.rhel6 fails on initdb

The following bug has been logged on the website:

Bug reference: 14954
Logged by: mbochenk
Email address: mbochenk(at)tibco(dot)com
PostgreSQL version: 9.6.6
Operating system: CentOS 6.9
Description:

Installing latest pg on CentOS 6 succeeds, however on 'sudo service
postgresql-9.6 initdb' the error in /var/lib/pgsql/9.6/pgstartup.log
shows:

'The files belonging to this database system will be owned by user
"postgres".
This user must also own the server process.

The database cluster will be initialized with locale "en_US.UTF-8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

initdb: directory "/var/lib/pgsql/9.6/data" exists but is not empty
If you want to create a new database system, either remove or empty
the directory "/var/lib/pgsql/9.6/data" or run initdb
with an argument other than "/var/lib/pgsql/9.6/data".'

Removed data/, removed package, reinstalled - same behaviour. Same for 9.5
and 9.3 (latest).

If using 9.6.6-2PGDG.rhel6/9.5.10-2PGDG.rhel6 (previous latest rpm) initdb
succeeds.

rpm packages for 9.6.6-3PGDG/9.5.10-3PGDG.rhel6 look like built on
2017-12-07, so this must be a new behaviour.

CentOS6 version:
lsb_release -a
LSB
Version: :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch
Distributor ID: CentOS
Description: CentOS release 6.9 (Final)
Release: 6.9
Codename: Final